Remote propellant casting process

ABSTRACT

A NOVEL PROCESS AND APPARATUS FOR CASTING HIGH ENERGY SOLID PROPELLANTS WITHOUT EXPOSURE TO PERSONNEL. THE PROCESS INVOLVES VACUUM CASTING OF THE PROPELLANT MIX FROM A PROPELLANT MIXER BOWL INTO A ROCKET MOTOR CASE UNDERNEATH THE MIXER BOWL BY PULLING A VACUUM ON THE MIXER BOWL FROM THE STRUCTURE CONTAINING THE ROCKET MOTOR CASE IN ORDER TO OPEN A DISCHARGE VALVE LOCATED BETWEEN THE MIXER BOWL AND THE ROCKET MOTOR. CHANNELING IS PREVENTED AND AIR EXCLUDED BY THE USE OF A FOLLOWER PLATE RESTING ON TOP OF THE PROPELLANT MIX.

Feb. 9, 1971 F. J. CAUDLE ET AL 3,562,364

REMOTE PROPELLANT CASTING PROCESS Filed May 6, 1968 Ford J. Caudle Joe S.Foster y K. Nipp Solon H. Morring Russell T. Smiih,

1NVENTOR5 3,562,364 REMOTE PROPELLANT CASTING PROCESS Ford J. Candle, Athens, Ala., Joe S. Foster, Newtown,

Pa, Bobby K. Nipp, Knoxville, Tenn., and Solon H.

Morring, New Hope, and Russell T. Smith, Decatur.

Alan, assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Army Filed May 6, 1968, Ser. No. 726,936 Int. Cl. C061? 21/00 US. Cl. 264-3 3 Claims ABSTRACT OF THE DISCLOSURE A novel process and apparatus for casting high energy solid propellants without exposure to personnel. The process involves vacuum casting of the propellant mix from a propellant mixer bowl into a rocket motor case underneath the mixer bowl by pulling a vacuum on the mixer bowl from the structure containing the rocket motor case in order to open a discharge valve located between the mixer bowl and the rocket motor. Channeling is prevented and air excluded by the use of a follower plate resting on top of the propellant mix.

BACKGROUND OF THE INVENTION This invention relates to a novel process and apparatus for casting high energy solid propellants, and in particular to such a process and apparatus which does not expose personnel.

During operations in which high energy solid propellants are either being moved, agitated, or under or pressure, the chances of an explosion are greatly increased. Accordingly, remote processing of high energy propellants has long been used to ensure safety to personnel. Additionally, remote processing of propellants may greatly increase propellant yields.

Accordingly, the principal object of this invention is to provide an improved remote process and apparatus for casting high energy solid propellants.

A particular object of this invention is to find such a process and apparatus which will greatly improve propellant yields.

SUMMARY OF THE INVENTION The process of this invention involves vacuum casting of a propellant mix into a rocket motor case or other container by pulling a vacuum on a propellant mixer bowl in order to open a mixer valve located between the mixer bowl and the rocket motor. Channeling is prevented and air excluded by the use of a follower plate resting on top of the propellant mix. The weight of propellant mix charged to the motor is monitored by a remote direct reading load cell. The mixer is cleaned by forcing solvent through a hole in the top of the follower plate and thereby forcing the follower plate back to the top of the mixer bowl.

BRIEF DESCRIPTION OF THE DRAWING These and other objects and advantages of this invention will become more easily understood and readily apparent from the following detailed description of this invention, of which the accompanying drawing forms an integral part.

In the drawing,

FIG. 1 is a cross-sectional view of the propellant mixing and casting apparatus of this invention with the mixer valve thereof shown in the open position.

FIG. 2 is a view taken along line 2-2 of FIG. 1; and,

States Patent FIG. 3 is a cross-sectional view of a mixer valve of the funnel is removed and spider plate is inserted therefor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the propellant mixing and casting apparatus of this invention includes a propellant mixer bowl 10 having a follower plate 12 at the top thereof. Propellant 14 is initially present in mixer bowl 10. Vacuum line 16 is attached to follower plate 12 and communicates with the top of mixer bowl and propellant mix 14 via hole 18. A bottom discharge valve 20 is located in the bottom of mixer It]. A funnel 19 with ribs 1% is secured by screws 17 to the mixer bowl 10. Pin 21 is attached to valve 20 to position the valve in a spaced position relative to ribs 19a when in the open position and to keep valve 20 from rotating. Mixer bowl 10 is connected with casting chamber 22 in casting can 24 by tubes 43 and 45. Rocket motor case 26 (or other container) is located in chamber 22 on top of plate 28 which, in turn, rests on ring 30. A small space normally exists between plate 28 and a plate 32. Plate 32 is attached to extendible rod 34, which is in turn attached to load cell 38. Load cell 38 is attached to a bushing 40, which is attached to cylinder 42. Fluid supply line 52 communicates with cylinder 42 and an electrical cable readout 54 is connected to load cell 38.

Vacuum line 44 communicates with the lower portion of chamber 26, and an air supply 46 communicates with air cylinder 46a. Clamp 47 surrounds flexible tubing 45 and is actuated by air cylinder 46ato clamp and close off flow through tubing 45.

Referring now to FIG. 3, a Teflon spider plate 48 is shown holding valve 20 in the up position. Spider plate 48 is held in the up position by three lugs (only one,

lug 50, of which is shown) which are clamped by screws 17.

In the process of this invention, discharge valve 20, is secured in the up (closed) position by spider plate 48, which is in turn secured by lug 50 and two other lugs (not shown). The propellant is mixed in a conventional manner, well known to those skilled in the art, in mixer bowl 10. This involves adding all of the liquid ingredients of the propellant to mixer bowl 10. Then as the liquid is mixed, the solid ingredients (e.g., aluminum and ammonium perchlorate powders) are slowly added to the propellant mix over a period of hours. For best results, it has been found highly desirable to further mix the propellant mix 14 under vacuum. When mixing is complete, follower plate 12 is inserted in the top of mixer bowl 10. Air is withdrawn from the top of mixer bowl 10 (between follower plate 12 and propellant mix 14) via hole 18 and vacuum line 16 by applying a vacuum to the latter. Thus, follower plate 12 is forced down against propellant mix 14. The vacuum is withdrawn and spider plate 48 is then removed by unfastening lug 50. Funnel 19 is then put into place and secured by screws 17. Valve 20 remains in the upper (closed) position due to the adhesive nature of propellant mix 14. However, if desired, a slight interference fit in valve 20 (or other conventional means) may be employed to retain valve 20 in place after the removal of the spider plate. Fluid is supplied to line 52 to extend rod 34, thereby raising plate 32 into contact with plate 28. A vacuum is then applied to casting chamber 22 via vacuum line 44. This causes discharge valve 20 to be moved down to the open (lower) position. Pin 21, attached to valve 20, and ribs 19:: insure that valve 20 will be spaced from funnel 19 sufiicient to allow propellant mix 14 to flow into rocket motor 26. Thus, the process of this invention is at the stage shown in FIG. 1. Propellant mix 14 continues to be vacuum cast into rocket motor case 26 (or other container). Follower plate 12 continues to rest on the top of propellant mix 14' as the level thereof in mixer bowl continues to fall. By resting on top of pro pellant mix 14, the follower plate prevents channeling and excludes air from propellant mix 14. The weight of propellant charged to motor 26 is monitored remotely by the direct reading load cell 38. When the desired weight of propellant mix 14 has been charged to motor 26, as indicated by electrical cable readout 54, air cylinder 46a is actuated to clamp flexible tubing 45 by means of clamp 47. This stops the flow of propellant mix 14 through tubing 45, by means of clamp 4-7. This stops the flow of propellant mix 14 through tubing 45, and before cleaning the mixer, fluid supply 52 is released in order to lower the load cell.

To clean the mixer, a solvent such as methylene chloride is forced through a Teflon solvent line (substituted for the vacuum line 16) and then through hole 18 in follower plate 12, thereby forcing follower plate 12 back to the top of mixer bowl 10. This has been found to be an excellent method of cleaning mixer bowl 10.

Before the next mixing and casting cycle is commenced,

spider plate 48 is secured to the mixer bowl 10 to holdvalve 20 in the closed position.

In the process of this invention, all operations are conducted remotely. This process is extremely versatile and can handle prepellants of widely varying viscosities (2000-1,000,000 cps. at room temperature). Propellant yields are greatly increased through the use of this process, propellant yields above 95% (in the motors) having being obtained thereby. The use of a follower plate also prevents channeling and adds to the cleanliness of the operation as well as increasing the propellant yield. Since casting is effected under vacuum, no air bubble problem exists and the need for a slit plate is eliminated.

Various other modifications and variations of the method and apparatus of this invention will become readily apparent to those skilled in the art in the light of the above teachings, which modifications and variations are within the spirit and scope of this invention.

4 What is claimed is: 1. The process of remotely casting a high energy propellant mix into a casting chamber from a propellant mixer comprising the steps of introducing a propellant r mix into a propellant mixer, placing a follower plate above said propellant mix and evacuating the space between said follower plate and said propellant mix to thereby cause said follower plate to be forced down against said propellant mix and remove any gas between said propellant mix and said follower plate, opening a discharge valve, said discharge valve being in fluid communication at one end thereof with said propellant mixer and at the other end thereof with a casting chamber formed by a casting can, said discharge valve being opened by applying second vacuum means in said casting chamber which is in air tight fluid communication with the other end of said discharge valve, thereby causing said propellant mix to flow under said second vacuum means into said casting chamber.

2. The process of claim 1 additionally comprising the step of casting said propellant mix into a motor case inside said casting can.

3. The process of claim 2 additionally comprising the step of remotely monitoring the amount of propellant cast into said motor case and stopping the flow of propellant into said motor case when a predetermined amount of propellant has been cast into said motor case.

References Cited UNITED STATES PATENTS 7/1966 Glick et al 2643X 3/1967 Brock et al 2643 US. Cl. X.R. l4942, 109 

